I was thinking -- not "taking back" -- but "carrying the offensive to the dirty-minded enemy", and -- in return for all the things in the language which they have besmirched and ruined -- taking away from them, one of their creations.
The problem with picking this particular phrase would be that the term 'friends with benefits' is a description of a type of relationship
rather than an innuendo, or dirty word, or term that has an alternate meaning. It's not the kind of phrase where you go "they're 'friends with benefits', nudge, nudge, wink, wink, giggle", but rather a label for a type of relationship
that would go along side things like casually dating
, or one night stand or seriously dating
, or living together.
She may not approve of that type of relationship
, but the effect of trying to re-purpose the label is not going to make that point - most people will react the way the OP did, that she's a naive old person who doesn't know the meaning of the term. If they realize she does know the meaning (or don't know her age), they'll think she's kind of creepy or weird.